Keys of this type with two encoded surfaces are known from the prior art, specifically as reversible keys in particular. Reversible keys are keys, the shaft of which has uniformly arranged profiles, guide grooves, depressions, elevations or/and notches on both sides. The key therefore in each case has the same features rotated about the longitudinal axis thereof and can therefore—independently of the side of the key which is pointing upwards—also be introduced into the keyway of the associated lock cylinder in a rotated fashion, which is not possible in the case of a normal key which has notches on one side.
As the codes on reversible keys are identical on both sides, for the most part in the lock, the codes are read on each side alternately, in order to reduce the number of sensing elements. In this context, the term “identical codes” means that the codes are the same on the respectively considered surfaces when the key is rotated about the longitudinal axis thereof.
In reversible keys of this type, the depiction of one side is sufficient however in order to be able to reproduce the key. This is disadvantageous with regards to modern reproduction methods (high-resolution smartphone cameras in combination with 3D printing), as illegal keys can easily be brought into circulation.